The present invention relates to a semiconductor laser of the type having a layer sequence formed as a heterostructure diode in which a substantially homogeneously doped laser active zone is enclosed on each of two sides by two semiconductor layers having respectively different dopings and provided with means for constricting the current flowing in the forward direction of the diode to a narrow strip-shaped region of the laser active zone.
Such semiconductor lasers are used, for example, in the optical data transmission art, as light transmitters for optical fibers.
One such semiconductor laser, as shown in FIG. 1, is disclosed in Federal Republic of Germany Offenlegungsschrift (DE-OS) No. 2,822,146 corresponding to U.S. Pat. No. 4,278,949 issued July 14th, 1981 to Peter Marschall et al, the subject matter of which is incorporated by reference. The layers 2, 3, 4 and 6 have here been grown epitaxially onto the substrate 1, with a trough-shaped recess 10 being etched in the upper layer 6 to suitably shape the diffusion region 7. The layers 2, 3, 4 and 6 are formed of InP, InGaAsP, InP and InP, respectively, and the substrate 1 is formed of InP. Generally, the diffusion region 7 is p-conductive so that, with a p-conductive layer 4 and an n-conductive layer 6, the current path is limited along the interface between layer 4 and layer 6. The electrically conductive contacts 8, 9 can be connected to electrical devices, not shown.
If such a semiconductor laser is dimensioned so that the emitted laser light lies in the longwave spectral range (wavelengths greater than 1.mu.), there occur annoying interferences during the so-called continuous wave operation of the semiconductor laser.